What 2010 does - and doesn't - tell us about 2012

From the NBC News political teamBy all indications, the president's party is heading for midterm losses tomorrow night that could be comparable to Democrats' defeat during the Republican Revolution of 1994. Some projections show a change of power in the House more powerful than any since the late 1940s.

According to the latest NBC/WSJ poll, the president's approval rating with likely voters is just 44 percent, and even worse among white voters, who make up the vast majority of voters in the districts up for grabs.

But -- as we've pointed out in this space before, and it bears repeating on the eve of the election -- even if Democrats suffer enormous midterm losses, people should be very careful about assuming that President Obama's presidential re-election chances will be imperiled.

First, it's the historical norm for a president's party to lose seats -- an average of 26 seats. Except for President George W. Bush, whose GOP saw modest gains in the cycle after the 9/11 terrorist attacks, every president since Harry Truman has seen his party lose seats in the middle of his first term.

That's a trend the president and his surrogates have obliquely acknowledged, even as they furiously stump nationwide to turn out their base.

"If everyone who fought for change in 2008 shows up to vote in 2010, we will win this election," Obama said yesterday in Ohio.

Data in the NBC/WSJ poll shows that he's probably correct.

Although Democrats are on the wrong end of an enthusiasm gap during this midterm election -- meaning that the voters who are most likely to go to the polls favor a Republican-led Congress by six percentage points -- when all registered voters are surveyed, that advantage drops to just two percent.

Just two weeks ago, registered voters actually favored a Democratic-held Congress by two points.

Another reason that Obama's 2012 re-election chances remain relatively high: His approval rating with key constituencies remains robust. Just shy of 90 percent of African-American voters approve of his job performance; Hispanics back him by 55 percent to 31 percent; he still has a net positive rating among voters under 35.

Those groups help in boosting the president's overall approval rating with all registered voters close to 50 percent, still making him a formidable opponent for any GOP challenger -- who will have to win the nomination by rising to the top of a crowded primary field.

Plus, remember some recent history: In 1982, when unemployment was above 10% for 13-straight months, Republicans lost 26 seats; in January 1983, Ronald Reagan's Gallup approval rating was just 35%, but Reagan went on to a landslide victory two years later.

In 1994, Democrats lost 54 House seats, second only -- since World War II -- to Harry Truman, who lost 55 House seats in 1946. Clinton also went on to a decisive re-election win in 1996.

Much of this, of course, depends -- on the economy, on the agenda, on who the Republican presidential nominee is. But it's important context when talking about what the results mean tomorrow night.